1. Field of the Invention
The present invention relates to a thermoplastic polyester resin composition which provides molded articles superior in impact resistance, heat resistance, cold resistance, and weather resistance.
2. Description of the Prior Art
Thermoplastic polyester, e.g. polyalkylene terephthalates, having superior mechanical properties, heat stability, weather resistance, electrical insulation properties, etc., are in use over extensive fields including electrical or electronic components, automotive parts, and so forth. However, their applications are considerably restricted because they are inferior in impact resistance, especially when notched. To automotive exterior and interior materials and housings of large electronic equipments, applications of these thermoplastic polyester resins have been investigated to take full advantage of their superior mechanical and thermal properties, but such application cannot be enough developed today because of their insufficient impact resistance and cold resistance. Various methods are proposed for improving the impact resistance of these thermoplastic polyester resins and are successful to some extent in this improvement but sacrifice other properties of the resins, so that such modified resins have found no plenty of practical applications. For instance, although the impact resistance of thermoplastic polyesters is improved by blending them with a diene rubber-modified resin, the heat stability and weather resistance, on the contrary, are deteriorated thereby to large extents. On the other hand, the blending with an acrylic rubber-modified resin results in slightest deterioration of the weather resistance but is little effective in improving the impact resistance at low temperatures. Olefin copolymers are also effective in improving the impact resistance of thermoplastic polyesters, but present problems such that the blending of such copolymers lowers other mechanical properties of the polyester and their dispersibility is poor, causing delamination. Hence, olefin copolymers also cannot be used for the blending.